In the last few years, the indie game scene has been bursting with great success. However, few have been as retro as Kickstarter success Shovel Knight. Inspired by great NES classic such as Megaman, Castlevania and Metroid, the game is a blast to play. The level design is creative, and the game play is well balanced. However, don't take my word for it, read the many great reviews.
The authors have been surprisingly open about their sales numbers. Although uncommon for game developers, it is a growing trend among indie developers. Even more impressive are the game design articles published on Gamasutra.
In the end, Shovel Knights is a great success for everyone. Yacht Club Games made a good amount of money from the sales. Other game developers benefit from the shared knowledge. And the players get a great game. If you haven't tried it out yet, check it out.
Edit: 15/10/2014 : Added Kickstarter reference.